We propose the application of serologic techniques for the identification and quantitation of base damage in DNA. This approach is extremely important since no method exists for the estimation of base damage at low doses. Current chemical methods lack sensitivity, are difficult to quantitate, and may introduce artifacts during hydrolysis. The scope of the present work is limited to adenine radiation products. The sensitivity and specificity which can be achieved, especially with a radioimmune assay will allow detection of base damage at very low, biologically significant doses. Total base damage and yields of specific products will be followed. Numerous methods have been reported for the preparation of nucleic acid base immunogens. Consequently, the problem of artifacts in this phase of the proposal can be dealt with by existing methodology. Base damage in irradiated cells can possibly be serologically determined without purification and hydrolysis of the DNA. These techniques will be extended to the study of irradiation products of all bases, and to damage induced by chemical mutagens and carcinogens. This work is basic to the understanding and possible control of radiation induced carcinogenesis. Alteration of the purine and pyrimidine bases of DNA may result in cellular changes which lead to somatic mutation and carcinogenesis.